The present invention relates to a kneader for kneading a viscous material such as plastic, rubber, etc., and more particularly to the arrangement of the rotor shafts thereof.
There is known a method for making the rotor shafts of a kneader, by which after the shafts have been lathed, blades separately made are welded to the shafts. According to this method, the welding heat generates thermal stress on the shafts. This may cause the shafts not to be axially aligned.
In a pressure-type kneader for kneading a material under a high pressure in an enclosed space, the material leaks from the kneading chamber to the outside or the material leaks in the kneading chamber to the spaces inside of the blades after passing through gaps, if any, between the shafts and the blades. Therefore, the kneader needs to be sealed against such material leakage.
Further, when the shafts are made separately from the blades, a corrosion resisting material such as ceramic, stainless steel, engineering plastic may be used as the blade material. When the blades made of such corrosion resisting material are to be secured to the shafts, it should not be allowed to use, in the kneading chamber, bolts, screws or other members which may be corroded.
Further, in the kneader a heat transfer medium is generally circulated inside of the blades to cool or heat a material to be kneaded. It is therefore preferable to provide wide spaces in the blade insides to enhance the heat conduction with respect to the blade surfaces.